The instant invention relates to automatic dry pipe sprinkler systems of the type used for fire protection, and more particularly to an accelerator for quickening the opening of a differential type of dry pipe (water control) valve in response to the operation of one or more sprinkler heads.
Basically, there are two predominant types of automatic fire protection sprinkler systems; a wet pipe system wherein the piping leading from its water control valve to the sprinkler heads is normally filled with water, and a dry pipe system wherein the piping leading from its water control valve to the sprinkler heads is pressurized with a gas until the water control (dry pipe) valve closing off the source of water from the system has been opened to introduce water into the piping leading to the sprinkler heads thereof. Wet pipe sprinkler systems offer the advantage of water being immediately discharged from an operated sprinkler. On the other hand, wet pipe sprinkler systems cannot be readily used in applications where there is a possibility that the system piping interconnecting the sprinkler head will be exposed to freezing temperatures. Accordingly, dry pipe sprinkler systems are normally used in applications where freezing temperatures can occur. Dry pipe sprinkler systems, however, have the drawback that because the piping thereof is normally filed with pressurized gas and not water, water is not immediately discharged from an operated sprinkler.
In dry pipe sprinkler systems, when a sprinkler head is operated, a portion of the gas flows out through the opened sprinkler head, causing a decrease in the pressure of the gas in the piping connected thereto. When the pressure of the gas in the piping drops to a certain level, the dry pipe valve automatically opens so that water can be introduced into the piping. However, because gas is a compressible medium, it takes a relatively substantial amount of time for the pressure of the gas in the piping to decay to a level which is sufficient to open the dry pipe valve connected thereto. Obviously, when a fire occurs, it is critical that water be delivered to an operated sprinkler as quickly as possible. Accordingly, the National Fire Protection Association Standard NFPA-13 requires that dry pipe sprinkler systems be constructed such that when the sprinkler head furthest from the dry pipe valve is operated, water will be delivered thereto within sixty seconds of the time of operation. For this reason, many dry pipe sprinkler systems require an accelerator which is utilized for sensing a slight but significant rate of decay in the dry pipe system gas pressure and for quickening the opening of the dry pipe valve connected thereto, in response to the pressure decay.
A differential type of a dry pipe valve is by definition constructed with two chambers; a main chamber which is exposed to system pressure and an intermediate chamber which is normally exposed to atmospheric pressure. Further, a differential type of dry pipe valve is designed such that when a fluid under a pressure of essentially the same value as the gas in the system is admitted to the intermediate chamber thereof, its channel between the source of water supply and the system will be opened. Accordingly, an accelerator is interconnected by piping between its inlet and the pressurized portion of the system and between its outlet and the intermediate chamber of the dry pipe valve such that when the accelerator is actuated, gas under pressure is admitted from the system to the intermediate chamber of the dry pipe valve to effect the opening of the latter.
Accelerators representing the closest prior art to the instant invention, of which the applicant is aware, are disclosed in the U.S. patents to Rowley U.S. Pat. No. 1,913,245; Herkimer U.S. Pat. No. 2,822,052; Zimmerman U.S. Pat. No. 3,685,586; and Shea U.S. Pat. No. 3,785,440. While these references do teach a variety of accelerator constructions, they do not teach an accelerator having the specific structural features and specific advantages of the accelerator of the instant invention, and hence they are believed to be of nothing more than general interest, as will hereinafter be made apparent.
Once water has been introduced into a dry pipe sprinkler system by opening of its dry pipe valve, the water can freely pass through the piping leading to the sprinkler heads thereof as well as the accelerator. While water and small quantities of debris which may be entrained in the water will not normally damage the exhaust valve element portion of the accelerator which is operative for opening the passageway between the system and the intermediate chamber of the dry pipe valve, it is important that the debris and/or water does not reach the components which effect the actuation of the accelerator. In this regard, most dry pipe valve accelerators are constructed with a first or differential chamber and a second or pilot chamber which communicate through a restriction which retards the equalization of the pressure of the gas in the two chambers and, by so doing, causes the actuation of the accelerator. It is essential for the reliable operation of an accelerator of this type that the restriction thereof be protected from debris and/or water which can clog it and substantially lower the rate of pressure equalization between the two chambers below the desired preset rate, and by so doing, cause the accelerator to unnecessarily actuate in response to inconsequential reductions in system pressure which can result from minor gas leaks or temperature drops. It is also desirable that any debris entrained within the water introduced to the system be kept from entering the second said chamber which normally encloses the actuation mechanism of the accelerator so that the freedom of movement of the mechanism will not be affected. The principal time of concern is when water is flowing into the system under pressure. However, a further desirable feature of dry pipe valve accelerators is that no debris and/or water be permitted to enter the second chamber or come in contact with the restriction after the flow of water into the system has been shut off and while all debris and water is being drained from the system as well as the piping interconnecting the accelerator with the system. None of the heretofore available dry pipe valve accelerators have reliably provided all of these features. Specifically, while some of the known accelerators have included means for protecting the internal components thereof from the pressurized water which is distributed throughout the system after opening of the dry pipe valve, none of the known accelerators have included means for reliably protecting the internal components which effect the actuation thereof from a relatively low pressure water which is present when the system is shut off and water is being drained from the system.
The instant invention provides a novel dry pipe valve accelerator which effectively overcomes this and other disadvantages of the heretofore known accelerators. In contrast to the previously known accelerators, the internal operating components of the accelerator of the instant invention are completely protected against debris and/or water under all high and low pressure conditions. Further, the accelerator of the instant invention includes a novel latching assembly which assures that once the accelerator has been actuated, the internal components thereof are maintained fully protected until the accelerator is manually reset and again rendered responsive to a decay in system pressure. Accordingly, once the accelerator has been actuated, the first and second internal chambers thereof and all of the internal components thereof, including the restriction element of the accelerator (all of which will hereinafter be more fully described), are fully protected against debris and/or water which might otherwise undesirably affect the operation of the accelerator. After the dry pipe sprinkler system has been shut down and drained such that it is apparent that all of the debris and/or water has been removed from the system, the accelerator of the instant invention can easily be reset by manipulation of a knob external to the accelerator so that the internal components of the accelerator are again rendered fully operative. Hence, for these reasons, as well as a number of other reasons which will hereinafter be set forth, it will become apparent that the accelerators of the instant invention represents a significant advancement in the art.
The accelerator of the instant invention comprises a housing having a first or differential chamber, a second or pilot chamber, and a valve body adjacent the second chamber, the body having a passage therethrough with an inlet end connectable by piping to the pressurized portion of a dry pipe sprinkler system and an outlet end connectable by piping to the intermediate chamber of a differential-type dry pipe valve, the housing also having a restriction joining the first and second chambers for providing retarded pressure equalization therebetween, an aperture between the second chamber and the inlet end of the passage, and a relief port between the second chamber and the exterior of the housing (i.e., atmosphere). An antiflood valve is provided in the second chamber and is alternatively positionable in open or closed positions thereof wherein said aperture is opened or closed, respectively, the antiflood valve being normally biased to the open position thereof. A relief valve is also provided in the second chamber and is alternatively positionable in open or closed positions thereof wherein said relief port is opened or closed, respectively, the relief valve being normally biased to the closed position thereof. A lever interconnecting the antiflood and relief valves maintains them in the opposite respective positions thereof. An actuator assembly that is positioned at the interface between the first and second chambers is movably responsive to a pressure decrease from the first chamber to the second chamber for rotating said lever and thereby moving the antiflood valve to the closed position thereof and, therefore, the relief valve to the open position thereof. Also provided in the accelerator is an exhaust valve element mounted in the housing which is alternatively positionable in open (tripped) or closed (set) positions thereof wherein the passage is opened or closed, respectively. The exhaust valve element is normally positioned in the closed position thereof when the antiflood valve is in the open position thereof, and it is constructed so that when the gas pressure in the second chamber is substantially equal to the gas pressure in the inlet end of the passage, the exhaust valve element is maintained in the closed position thereof by a combination of the force exerted by a spring acting on the lever and by the pressure in the second chamber. The exhaust valve element is, however, responsive to a condition wherein the pressure in the second chamber is substantially less than the pressure in the inlet end of the passage for movement of the exhaust valve element to the open position thereof whereby the passage between the inlet and outlet ends of the accelerator is made open. Accordingly, when the actuator assembly moves the antiflood valve towards the closed position thereof and the relief valve to the open position thereof, whereby the pressure in the second chamber is decreased to essentially atmospheric pressure, the pressure differential created between the inlet end of the passage and the second chamber causes the exhaust valve element to be moved to the open (tripped) position thereof. The preferred embodiment of the accelerator further comprises a latching member which is engageable with said lever, by the action of the exhaust valve element moving to the open position, to releasably retain it (by externally manipulative means) in a position wherein the antiflood valve is maintained in a closed position in the aperture, the relief valve is maintained in an open position from the relief port and the exhaust valve element is maintained in an open (tripped) position in the passage.
In the operation of the accelerator, the antiflood valve is normally maintained in the open position so that the pressure in the inlet end of the passage is essentially equal to the pressure in the second chamber whereby the exhaust valve element is maintained in a closed position in the passage. When a sprinkler head in the system is operated so that the pressure in the system commences to decay, the pressure in the second chamber of the accelerator decreases, because it is open to the system through the aperture. Since there is a restriction joining the first and second chambers of the accelerator, the pressure in the first chamber does not decrease as rapidly as the pressure in the second chamber and, therefore, a pressure differential is created between the first and second chambers. When this pressure differential reaches a predetermined level, the actuator assembly of the accelerator acts on the lever to move the antiflood valve towards its closed position in the aperture and to move the relief valve to an open position from the relief port whereby the second chamber is opened to the atmosphere. As a result, a substantial decrease in the pressure in the second chamber relative to the pressure in the inlet end of the passage is created, and the exhaust valve element can no longer be retained in the closed position thereof by the pressure in the second chamber. Consequently, the pressure in the inlet end of the passage moves the exhaust valve element to the open position thereof. Accordingly, the accelerator admits gas under pressure from the system to the intermediate chamber of the differential type of dry pipe valve to effect the opening of the latter. After the dry pipe valve has been opened, the passage in the accelerator is open to the sprinkler system (at its inlet end) so that water can enter the passage. It will be noted, however, that while water can enter the passage, it cannot reach either of the first or second chambers of the accelerator so that all of the operative components of the accelerator are also protected from debris, which could be carried by the water. Further, since the accelerator includes means for releasably retaining it in a position wherein the antiflood valve is in a closed position in the aperture, water cannot enter the second chamber regardless of the system pressure, and therefore the operative components of the accelerator, including the restriction, are protected from exposure to debris and/or water, even when and after the system is shut down.
Accordingly, it is a primary object of the instant invention to provide an effective and reliable differential-type dry pipe valve accelerator for dry pipe sprinkler systems.
Another object of the instant invention is to provide a differential-type dry pipe valve accelerator wherein the operative components thereof are fully protected from debris and/or water by the closing of an internal antiflood valve, even when and after the sprinkler system connected to the accelerator are shut down.
A still further object of the instant invention is to provide an accelerator which must be reset by manually manipulating an external reset element before it can be reused.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.